Fiber placement machines such as the ones manufactured by Cincinnati Milacron Inc. are well known in the field of manufacture of composite material pieces. In these machines, a plurality of tows of fiber preimpregnated with resin which come from various reels are led in the form of a band of tows to an application head from which they are applied on a mould for shaping the pieces with the desired shapes.
Patents U.S. Pat. Nos. 5,022,952, 5,273,614 and EP 0 535264 A1 incorporated herein by reference, describe several features of the tow band guiding system.
Fiber placement machines are particularly used for placing layers of composite material on a contoured mould, the tows being very thin so as to be adapted to the desired contoured shapes.
The material of the tows is a preimpregnated material, a mixture of fibrous reinforcement and polymeric matrix of a sticky nature.
The tows, which can have a width of 3.2 mm for example, circulate through the fiber placement machine in the form of a band of a plurality of tows, for example 32 tows, to an application head in which the systems of cutting, clamping and advancing/restarting of the material are integrated such that the lay-up of the piece is carried out according to previously established patterns.
Until the band of tows reaches the application head, it passes through very narrow channels and guides for each tow for controlling its movements, causing a certain degree of fuzz-balls, dry fibers, dust, and excess surface resin and dirt to be generated due to the simple friction of the material in its passage through said guiding channels.
In turn, said defects can be originally present in the tows themselves because it is difficult to avoid them completely during their manufacture, especially in the case of very narrow tows requiring a high precision in the impregnation and cutting operations.
This excess of fibers and fluff causes jamming of the material in its passage through said guiding channels, causing a high rate of machine standstills in order to clean the machine, and therefore, a dramatic decrease of productivity thereof that can be estimated at around 30%, i.e. 30% of the total working time is required for maintenance.
In order to solve this drawback, refrigerating and dehumidifying both the working area and the application head of the fiber placement machine has been proposed but even though this reduces the drawback, it does not eliminate it because it is not possible to completely cool the working area.
The object of the present invention consists of providing a satisfactory solution to the aforementioned drawback.